Exemplary embodiments of the present invention relate to a mobile communications system, a gateway device, and a communication method.
In Long Term Evolution (LTE) mobile communications systems using Evolved Packet Core (EPC) as the core network, the location information of a mobile station is used when determining routing of an emergency call (“Functional stage 2 description of Location Services (LCS)” [3GPP TS23.271 v10.2.0] and “IP Multimedia Subsystem (IMS) emergency sessions” [3GPP TS23.167 v11.4.0]). As the location information, the identifier (cell identity) of a cell where the mobile station is located is used in some cases.
On the other hand, in recent mobile communications systems, there are cases that provide a femtocell service by introducing a small radio base station called a femto base station, in addition to the existing radio base station. In LTE mobile communications systems, the femto base station is called Home evolved Node B (HeNB). The area of the cell covered by the femto base station is several meters to several tens of meters in general. Further, a large number of femto base stations are deployed in the system in most cases. This is obvious from the fact that one telecommunications carrier needs to support at least one hundred and twenty-five million CSG (Closed Subscriber Group) identifiers according to “Service requirements for Home Node B (HNB) and Home eNode B (HeNB)” [3GPP TS22.220 v11.3.0], which describes the service requirements for HeNB.
Further, in the architecture specified by Third Generation Partnership Project (3GPP), there is a case where Home evolved Node B Gateway (HeNB-GW) is optionally placed between HeNB and Mobility Management Entity (MME), which is the core network node in the upper level. The use of an interface between HeNB and HeNB-GW and MME is specified as S1 Application Protocol (S1AP) by “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP)” [3GPP TS36.413 v10.3.0].
The above-described background art has the following issues.
For example, at the time of making a call connection for an emergency call, the following problem occurs when searching for Public Safety Answering Point (PSAP), which is the destination to which the emergency call is to be routed on the core network side, based on the identifier of the cell to which the mobile station belongs. Specifically, because a large number of HeNBs exist in the LTE femto system as described above, it takes a long processing time when searching for PSAP based on the cell identifier (ECGI: E-UTRAN Cell Global Identifier) which has different values for different HeNBs. Further, because a large number of communications occur between devices in the network, a heavy load is placed on the network.
The same problem occurs when performing the operation related to charging or lawful intercept by using ECGI as the location information of a mobile station. Further, the same problem occurs also when performing the operation for an emergency call, charging or lawful intercept by using Tracking Area Identity (TAI) instead of ECGI.
However, none of the above related art teaches a means of solving at least one of the above problems or a message interface between devices. Thus, an object of certain exemplary embodiments is to provide a mobile communications system, a gateway device, and a communication method capable of solving any of the above issues.